Chromatic aberration of the Selfoc lens as an imaging system

1980 ◽  
Vol 19 (7) ◽  
pp. 1052 ◽  
Author(s):  
Kouichi Nishizawa
Keyword(s):  
Imaging System ◽  
Chromatic Aberration

New Aspects in the Design of Electron Optical Magnification Systems

1972 ◽  
Vol 30 ◽  
pp. 606-607
Author(s):  
Willem H.J. Andersen
Keyword(s):  
Electron Microscope ◽  
Imaging System ◽  
Chromatic Aberration ◽  
Research Tool ◽  
Energy Losses ◽  
Objective Lens ◽  
Theoretical Limit ◽  
Optical Magnification ◽  
Chromatic Aberrations ◽  
High Degree

Electron microscope design, and particularly the design of the imaging system, has reached a high degree of perfection. Present objective lenses perform up to their theoretical limit, while the whole imaging system, consisting of three or four lenses, provides very wide ranges of magnification and diffraction camera length with virtually no distortion of the image. Evolution of the electron microscope in to a routine research tool in which objects of steadily increasing thickness are investigated, has made it necessary for the designer to pay special attention to the chromatic aberrations of the magnification system (as distinct from the chromatic aberration of the objective lens). These chromatic aberrations cause edge un-sharpness of the image due to electrons which have suffered energy losses in the object.There exist two kinds of chromatic aberration of the magnification system; the chromatic change of magnification, characterized by the coefficient Cm, and the chromatic change of rotation given by Cp.

Electron Holography Improving Transmission Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 208-209
Author(s):  
Hannes Lichte
Keyword(s):  
Electron Microscopy ◽  
Transfer Functions ◽  
Imaging System ◽  
Spherical Aberration ◽  
Image Plane ◽  
Chromatic Aberration ◽  
Object Wave ◽  
Objective Lens ◽  
Electron Holography ◽  
Wave Aberration

Generally, the electron object wave o(r) is modulated both in amplitude and phase. In the image plane of an ideal imaging system we would expect to find an image wave b(r) that is modulated in exactly the same way, i. e. b(r) =o(r). If, however, there are aberrations, the image wave instead reads as b(r) =o(r) * FT(WTF) i. e. the convolution of the object wave with the Fourier transform of the wave transfer function WTF . Taking into account chromatic aberration, illumination divergence and the wave aberration of the objective lens, one finds WTF(R) = Echrom(R)Ediv(R).exp(iX(R)) . The envelope functions Echrom(R) and Ediv(R) damp the image wave, whereas the effect of the wave aberration X(R) is to disorder amplitude and phase according to real and imaginary part of exp(iX(R)) , as is schematically sketched in fig. 1.Since in ordinary electron microscopy only the amplitude of the image wave can be recorded by the intensity of the image, the wave aberration has to be chosen such that the object component of interest (phase or amplitude) is directed into the image amplitude. Using an aberration free objective lens, for X=0 one sees the object amplitude, for X= π/2 (“Zernike phase contrast”) the object phase. For a real objective lens, however, the wave aberration is given by X(R) = 2π (.25 Csλ3R4 + 0.5ΔzλR2), Cs meaning the coefficient of spherical aberration and Δz defocusing. Consequently, the transfer functions sin X(R) and cos(X(R)) strongly depend on R such that amplitude and phase of the image wave represent only fragments of the object which, fortunately, supplement each other. However, recording only the amplitude gives rise to the fundamental problems, restricting resolution and interpretability of ordinary electron images:

Modeling and design of a multichannel chromatic aberration compensated imaging system

2015 ◽  
Author(s):  
Gebirie Y. Belay ◽  
Heidi Ottevaere ◽  
Michael Vervaeke ◽  
Jürgen Van Erps ◽  
Hugo Thienpont
Keyword(s):  
Imaging System ◽  
Chromatic Aberration

scholarly journals Eye tracking-based estimation and compensation of chromatic offsets for multi-wavelength retinal microstimulation with foveal cone precision

2019 ◽  
Author(s):  
Niklas Domdei ◽  
Michael Linden ◽  
Jenny L. Reiniger ◽  
Frank G. Holz ◽  
Wolf M. Harmening
Keyword(s):  
Adaptive Optics ◽  
Imaging System ◽  
Chromatic Dispersion ◽  
Photoreceptor Cells ◽  
Chromatic Aberration ◽  
Eye Position ◽  
Calibration Data ◽  
Multi Wavelength ◽  
In Vivo Testing

AbstractMulti-wavelength ophthalmic imaging and stimulation of photoreceptor cells requires consideration of chromatic dispersion of the eye, manifesting in longitudinal and transverse chromatic aberrations. Current image-based techniques to measure and correct transverse chromatic aberration (TCA) and the resulting transverse chromatic offset (TCO) in an adaptive optics retinal imaging system are precise, but lack compensation of small but significant shifts in eye position occurring during in vivo testing. Here we present a method that requires only a single measurement of TCO during controlled movements of the eye to map retinal chromatic image shifts to the image space of a pupil camera. After such calibration, TCO can be compensated by continuously monitoring eye position during experimentation and by interpolating correction vectors from a linear fit to the calibration data. The average change rate of TCO per head shift and the correlation between Kappa and the individual foveal TCA are close to the expectations based on a chromatic eye model. Our solution enables continuous correction of TCO with high spatial precision and avoids high light intensities required for re-measuring TCO after eye position changes, which is necessary for foveal cone-targeted psychophysical experimentation.

scholarly journals STUDY ON HIGH RESOLUTION MEMBRANE-BASED DIFFRACTIVE OPTICAL IMAGING ON GEOSTATIONARY ORBIT

2017 ◽  
Vol XLII-1/W1 ◽  
pp. 371-375 ◽  
Author(s):  
J. Jiao ◽  
B. Wang ◽  
C. Wang ◽  
Y. Zhang ◽  
J. Jin ◽  
...  
Keyword(s):  
High Resolution ◽  
Optical Imaging ◽  
Diffraction Efficiency ◽  
Imaging System ◽  
Optical Element ◽  
Chromatic Aberration ◽  
Geostationary Orbit ◽  
Optical Elements ◽  
Optical Imaging System ◽  
High Diffraction

Diffractive optical imaging technology provides a new way to realize high resolution earth observation on geostationary orbit. There are a lot of benefits to use the membrane-based diffractive optical element in ultra-large aperture optical imaging system, including loose tolerance, light weight, easy folding and unfolding, which make it easy to realize high resolution earth observation on geostationary orbit. The implementation of this technology also faces some challenges, including the configuration of the diffractive primary lens, the development of high diffraction efficiency membrane-based diffractive optical elements, and the correction of the chromatic aberration of the diffractive optical elements. Aiming at the configuration of the diffractive primary lens, the “6+1” petal-type unfold scheme is proposed, which consider the compression ratio, the blocking rate and the development complexity. For high diffraction efficiency membrane-based diffractive optical element, a self-collimating method is proposed. The diffraction efficiency is more than 90 % of the theoretical value. For the chromatic aberration correction problem, an optimization method based on schupmann is proposed to make the imaging spectral bandwidth in visible light band reach 100 nm. The above conclusions have reference significance for the development of ultra-large aperture diffractive optical imaging system.

scholarly journals Chromatic Aberration in Digital Photomicrographs from Microscopes Requiring Compensating Eyepieces

2004 ◽  
Vol 12 (4) ◽  
pp. 34-37 ◽  
Author(s):  
Ted Clarke
Keyword(s):  
Refractive Index ◽  
White Light ◽  
Imaging System ◽  
Chromatic Aberration ◽  
Focal Points ◽  
Single Lens ◽  
Chromatic Aberrations ◽  
Different Color ◽  
Lateral Chromatic Aberration ◽  
Color Components

Chromatic aberrations are defects in an imaging system caused by the fact that different wavelengths or colors of light are refracted by different amounts. There are two types of chromatic aberration: longitudinal and lateral. Longitudinal Chromatic Aberration arises when a lens fails to focus various colors sharply in the same plane. If white light is used, the resulting image will be unsharp due to the different focal points of its component colors. Some colors will be in focus (and therefore sharp) and other colors will be out of focus. Lateral Chromatic Aberration results in a lateral shift of the different color components of an image as a single lens with a fixed refractive index will disperse each color by different amounts. This results in color stripes at slightly different magnifications, much like a rainbow, around hard edges and a general softening or decrease in resolution in all areas.

scholarly journals A Color Restoration Algorithm for Diffractive Optical Images of Membrane Camera

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1053
Author(s):  
Yanlei Du ◽  
Xiaofeng Yang ◽  
Yiping Ma ◽  
Chunxue Xu
Keyword(s):  
Computational Efficiency ◽  
Imaging System ◽  
Chromatic Aberration ◽  
Earth Orbit ◽  
Diffractive Imaging ◽  
Optical Images ◽  
Geo Satellite ◽  
Restoration Algorithm ◽  
Color Restoration ◽  
Algorithm Framework

In order to verify the technology of the membrane diffractive imaging system for Chinese next generation geo-stationary earth orbit (GEO) satellite, a series of ground experiments have been carried out using a membrane optical camera with 80 mm aperture (Φ80) lens. The inherent chromatic aberration due to diffractive imaging appears in the obtained data. To address the issue, an effective color restoration algorithm framework by matching, tailoring, and non-linearly stretching the image histograms is proposed in this letter. Experimental results show the proposed approach has good performances in color restoration of the diffractive optical images than previous methods. The effectiveness and robustness of the algorithm are also quantitatively assessed using various color deviation indexes. The results indicate that the chromatic aberration of diffractive images can be effectively removed by about 85%. Also, the proposed method presents reasonable computational efficiency.

Automatic White Balance Algorithm of Airborne Camera

2014 ◽  
Vol 668-669 ◽  
pp. 1050-1054
Author(s):  
Hui Nan Guo ◽  
Qing Liu ◽  
Lei Yang ◽  
Hua Wang ◽  
Xiao Dong Zhao ◽  
...  
Keyword(s):  
Digital Imaging ◽  
Imaging System ◽  
Chromatic Aberration ◽  
Input Image ◽  
Color Temperature ◽  
White Balance ◽  
Digital Imaging System ◽  
Different Color ◽  
Automatic White Balance

Automatic white balance algorithm (AWB) is significant for color temperature restoration of digital imaging system. According to the limitations and disadvantages of existing traditional white balance methods, in this paper a new AWB algorithm for airborne camera is proposed. Using RGB and histogram information divide the input image into different color character regions; according to the color richness level, adopt different white balance algorithms to achieve chromatic aberration adjustment. Experiment results show the effectiveness of the proposed AWB algorithm for airborne camera.

Sign in / Sign up

Export Citation Format

Share Document